From: "Clément Léger" <cleger@rivosinc.com>
To: Damien Le Moal <dlemoal@kernel.org>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Cc: "Conor Dooley" <conor.dooley@microchip.com>,
"Andrew Jones" <ajones@ventanamicro.com>,
"Björn Töpel" <bjorn@rivosinc.com>,
"Atish Patra" <atishp@rivosinc.com>
Subject: Re: [PATCH] riscv: deprecate CONFIG_MMU=n
Date: Mon, 26 Feb 2024 15:59:05 +0100 [thread overview]
Message-ID: <90b440e9-65b1-4482-88d4-f06e76863aa6@rivosinc.com> (raw)
In-Reply-To: <07675649-181a-4509-a595-d7ff9230e402@kernel.org>
On 26/02/2024 15:57, Damien Le Moal wrote:
> On 2024/02/26 6:06, Clément Léger wrote:
>> Deprecation of NOMMU support for riscv was discussed during LPC 2023
>> [1]. Reasons for this involves lack of users as well as maintenance
>> efforts to support this mode. psABI FDPIC specification also never
>> made it upstream and last public messages of this development seems to
>> date back from 2020 [2]. Plan the deprecation to be done in 2 years from
>> now. Mark the Kconfig option as deprecated by adding a new dummy option
>> which explicitly displays the deprecation in case of CONFIG_MMU=n. This option
>> is selected indirectly by CONFIG_RISCV_M_MODE since an option can not
>> select another one directly with a "select" in case of such CONFIG=n.
>> Additionally, display a pr_err() message at boot time in case of NOMMU
>> build to warn about upcoming deprecation.
>>
>> Link: https://lpc.events/event/17/contributions/1478/ [1]
>> Link: https://groups.google.com/a/groups.riscv.org/g/sw-dev/c/ZjYUJswknQ4/m/WYRRylTwAAAJ [2]
>> Signed-off-by: Clément Léger <cleger@rivosinc.com>
>>
>> ---
>> arch/riscv/Kconfig | 8 ++++++++
>> arch/riscv/kernel/setup.c | 4 ++++
>> 2 files changed, 12 insertions(+)
>>
>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>> index bffbd869a068..8da58c102d3f 100644
>> --- a/arch/riscv/Kconfig
>> +++ b/arch/riscv/Kconfig
>> @@ -221,6 +221,7 @@ config ARCH_MMAP_RND_COMPAT_BITS_MAX
>> # set if we run in machine mode, cleared if we run in supervisor mode
>> config RISCV_M_MODE
>> bool
>> + select NOMMU
>> default !MMU
>>
>> # set if we are running in S-mode and can use SBI calls
>> @@ -236,6 +237,13 @@ config MMU
>> Select if you want MMU-based virtualised addressing space
>> support by paged memory management. If unsure, say 'Y'.
>>
>> +config NOMMU
>> + depends on !MMU
>> + bool "NOMMU kernel (DEPRECATED)"
>> + help
>> + NOMMU kernel is deprecated and is scheduled for removal by
>> + the beginning of 2027.
>
> 2 years from now is 2026...
Guess I'm a bit tired -_-'
>
>> +
>> config PAGE_OFFSET
>> hex
>> default 0xC0000000 if 32BIT && MMU
>> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
>> index 4f73c0ae44b2..8799816ef0a6 100644
>> --- a/arch/riscv/kernel/setup.c
>> +++ b/arch/riscv/kernel/setup.c
>> @@ -295,6 +295,10 @@ void __init setup_arch(char **cmdline_p)
>> riscv_set_dma_cache_alignment();
>>
>> riscv_user_isa_enable();
>> +
>> +#if !defined(CONFIG_MMU)
>
> if (!IS_ENABLED(CONFIG_MMU))
>
> would be more elegant here...
Sure.
>
>> + pr_err("RISC-V NOMMU support is deprecated and scheduled for removal by the beginning of 2027\n");
>
> Why pr_err() ? pr_warn() seems more appropriate.
Agreed.
Thanks,
Clément
>
>> +#endif
>> }
>>
>> bool arch_cpu_is_hotpluggable(int cpu)
>
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next prev parent reply other threads:[~2024-02-26 14:59 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-26 14:06 [PATCH] riscv: deprecate CONFIG_MMU=n Clément Léger
2024-02-26 14:57 ` Damien Le Moal
2024-02-26 14:59 ` Clément Léger [this message]
2024-02-26 15:01 ` Damien Le Moal
2024-02-26 15:14 ` Samuel Holland
2024-02-26 15:25 ` Clément Léger
2024-02-26 16:02 ` Conor Dooley
2024-02-26 19:00 ` Charles Lohr
2024-02-26 21:29 ` Conor Dooley
2024-02-27 9:11 ` Clément Léger
2024-02-27 16:38 ` Palmer Dabbelt
2024-03-14 12:46 ` Jisheng Zhang
2024-03-14 13:02 ` Jisheng Zhang
2024-03-25 16:59 ` Jisheng Zhang
2024-03-26 20:25 ` Charles Lohr
2024-03-27 1:14 ` Jisheng Zhang
2024-03-27 1:34 ` Charles Lohr
2024-03-27 3:40 ` Jisheng Zhang
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